[Intrinsic UV-fluorescence of proteins as a tool for studying their dynamics]

A review of literature and our own data on intramolecular mobility of aromatic amino acids in proteins are presented. The necessity to take into account a possible existence of the nanosecond intramolecular mobility with the rotational relaxation time independent of solvent viscosity is pointed out. A comparison of spectral and polarizational characteristics of a number of proteins allowed to solve the problem of the mobility of tryptophan residues localized in the inner regions of macromolecules. According to experimental data, such tryptophan residues can be even more mobile than those located closer to the surface but in the surrounding of polar groups. It is most evident when comparing the intramolecular mobility of tryptophan residues of native proteins and some proteins in the intermediate state of the "molten globule" type. The comparison of experimental data with molecular dynamic simulations contributes substantially to the concepts of tryptophan residue mobility in proteins.